U.S. Pat. No. 6,507,633 B1 discloses a computed tomography system, which reconstructs an initial image of a region of interest from measured energy-dependent projection data. The initial image is segmented into several segments, wherein each segment represents another kind of material. For example, one segment can represent bones and another segment can represent soft tissue of a patient. A model for generating calculated energy-dependent projection data is used, which takes the different absorption distributions of the different kind of materials in the different segments into account, and deviations of the calculated energy-dependent projection data from the measured-projection data are minimized by modifying the different absorption distributions of the different kinds of materials in the different segments resulting in an image of the region of interest.
This reconstruction of an image of a region of interest is based on an initial segmentation. A segmentation of a computed tomography images is often inaccurate, in particular, if parts of an object have to be segmented which have almost the same image values leading to artifacts in the finally reconstructed image. In addition, a segmentation of an initial image is very time consuming.